This disclosure relates generally to display systems. More particularly, but not by way of limitation, this disclosure relates to techniques for properly rending text into a region of the display that may move arbitrarily from region to region on the display.
In some modern display systems an extra buffer (aka, a side buffer) may be used to store material that can move from one region of a display to another region (aka, dynamic material). When the material contained in the side buffer is moved, the entire side buffer may be blended into the background of the second region. While this approach works well much of the time, it does not work well when text is part of the information stored in the side buffer. To properly render text, it is necessary to know what is behind the text. This is why input to a text render pipeline includes the R (red), G (green), B (blue) and alpha (transparency) of each text character plus each character's RGB glyph-mask (i.e., 7 inputs). Side buffers have only 4 channels: R, G, B and alpha. As a result, once text is rendered into a side buffer it is no longer possible to render that text onto the screen properly as its glyph-mask information is no longer available.